Power Management Introduction; Power Modes - Texas Instruments CC253x User Manual

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4.1

Power Management Introduction

Different operating modes, or power modes, are used to allow low-power operation. Ultralow-power
operation is obtained by turning off the power supply to modules to avoid static (leakage) power
consumption and also by using clock gating and turning off oscillators to reduce dynamic power
consumption.
The five various operating modes (power modes) are called active mode, idle mode, PM1, PM2, and PM3
(PM1, PM2, and PM3 are also referred to as sleep modes). Active mode is the normal operating mode,
whereas PM3 has the lowest power consumption. The impact of the different power modes on system
operation is shown in
Power Mode
Configuration
Active or idle mode
PM1
PM2
PM3
Active mode: The fully functional mode. The voltage regulator to the digital core is on, and either the 16-
MHz RC oscillator or the 32-MHz crystal oscillator or both are running. Either the 32-kHz RCOSC or the
32-kHz XOSC is running.
Idle mode: Identical to active mode, except that the CPU core stops operating (is idle).
PM1: The voltage regulator to the digital part is on. Neither the 32-MHz XOSC nor the 16-MHz RCOSC is
running. Either the 32-kHz RCOSC or the 32-kHz XOSC is running. The system goes to active mode on
reset, an external interrupt, or when the Sleep Timer expires.
PM2: The voltage regulator to the digital core is turned off. Neither the 32-MHz XOSC nor the 16-MHz
RCOSC is running. Either the 32-kHz RCOSC or the 32-kHz XOSC is running. The system goes to active
mode on reset, an external interrupt, or when the Sleep Timer expires.
PM3: The voltage regulator to the digital core is turned off. None of the oscillators is running. The system
goes to active mode on reset or an external interrupt.
The POR is active in PM2 and PM3, but the BOD is powered down, which gives limited voltage
supervision. If the supply voltage is lowered to below 1.4 V during PM2 or PM3, at temperatures of 70°C
or higher, and then brought back up to good operating voltage before active mode is re-entered, registers
and RAM contents that are saved in PM2 or PM3 may become altered. Hence, care should be taken in
the design of the system power supply to ensure that this does not occur. The voltage can be periodically
supervised accurately by entering active mode, as a BOD reset is triggered if the supply voltage is below
approximately 1.7 V.
The CC2533 and CC2541 have functionality to perform automatically a CRC check of the retained
configuration register values in PM2 and PM3 to check that the device state was not altered during sleep.
The bits in SRCRC.CRC_RESULT indicate whether there were any changes, and by enabling
SRCRC.CRC_RESET_EN, the device immediately resets itself with a watchdog reset if
SRCRC.CRC_RESULT is not 00 (= CRC of retained registers passed) after wakeup from PM2 or PM3. The
SRCRC register also contains the SRCRC.FORCE_RESET bit that can be used by software to trigger a
watchdog reset immediately to reboot the device.
For CC2533 and CC2541, additional analog reset architecture adds another brownout detector (the
3VBOD) that senses on the unregulated voltage. The purpose of this 3VBOD is to reduce the current
consumption of the device when supplied with voltages well below the operating voltage.
SWRU191F – April 2009 – Revised April 2014
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Table 4-1, together with voltage regulator and oscillator options.
Table 4-1. Power Modes
High-Frequency Oscillator
A 32-MHz XOSC
B 16-MHz RCOSC
A or B
None
None
None
Copyright © 2009–2014, Texas Instruments Incorporated
Power Management Introduction
Low-Frequency Oscillator
C 32-kHz XOSC
D 32-kHz RCOSC
C or D
C or D
C or D
None
Power Management and Clocks
Voltage Regulator
(Digital)
ON
ON
OFF
OFF
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